Electrosurgical Devices with Directional Radiation Pattern

ABSTRACT

A device for directing energy to a target volume of tissue includes an antenna assembly and an elongated body member. The elongated body member includes a proximal end portion and a distal end portion, wherein the proximal and distal end portions define a longitudinal axis. The elongated body member has a chamber defined therein that extends along the longitudinal axis, and a body wall surrounding the chamber. An antenna assembly is disposed in the chamber. The elongated body member also includes an opening in the body wall to allow energy radiated from the antenna assembly to transfer into the target volume of tissue.

BACKGROUND

1. Technical Field

The present disclosure relates to electrosurgical devices suitable foruse in tissue ablation applications and, more particularly, toelectrosurgical devices with directional radiation patterns.

2. Discussion of Related Art

Treatment of certain diseases requires the destruction of malignanttissue growths, e.g., tumors. Electromagnetic radiation can be used toheat and destroy tumor cells. Treatment may involve inserting ablationprobes into tissues where cancerous tumors have been identified. Oncethe probes are positioned, electromagnetic energy is passed through theprobes into surrounding tissue.

In the treatment of diseases such as cancer, certain types of tumorcells have been found to denature at elevated temperatures that areslightly lower than temperatures normally injurious to healthy cells.Known treatment methods, such as hyperthermia therapy, heat diseasedcells to temperatures above 41° C. while maintaining adjacent healthycells below the temperature at which irreversible cell destruction mayoccur. These methods involve applying electromagnetic radiation to heat,ablate and/or coagulate tissue. Microwave energy is sometimes utilizedto perform these methods. Other procedures utilizing electromagneticradiation to heat tissue also include coagulation, cutting and/orablation of tissue.

Electrosurgical devices utilizing electromagnetic radiation have beendeveloped for a variety of uses and applications. A number of devicesare available that can be used to provide high bursts of energy forshort periods of time to achieve cutting and coagulative effects onvarious tissues. There are a number of different types of apparatus thatcan be used to perform ablation procedures. Typically, microwaveapparatus for use in ablation procedures include a microwave generator,which functions as an energy source, and a microwave surgical instrument(e.g., microwave ablation probe) having an antenna assembly fordirecting the energy to the target tissue. The microwave generator andsurgical instrument are typically operatively coupled by a cableassembly having a plurality of conductors for transmitting microwaveenergy from the generator to the instrument, and for communicatingcontrol, feedback and identification signals between the instrument andthe generator.

There are several types of microwave antenna assemblies for the ablationof tissue, such as monopole, dipole and helical. In monopole and dipoleantenna assemblies, microwave energy radiates perpendicularly away fromthe axis of the conductor. Monopole antenna assemblies include a singleelongated conductor whereas a typical dipole antenna assembly includestwo elongated conductors, which are linearly aligned and positionedend-to-end relative to one another with an electrical insulator placedtherebetween. Helical antenna assemblies include a helically-shapedconductor connected to a ground plane. Helical antenna assemblies canoperate in a number of modes, such as normal mode (broadside), in whichthe field radiated by the helix is maximum in a perpendicular plane tothe helix axis, and axial mode (end fire), in which maximum radiation isalong the helix axis.

A microwave transmission line typically includes a long, thin innerconductor that extends along a longitudinal transmission line axis andsurrounded by a dielectric material and is further surrounded by anouter conductor around the dielectric material such that the outerconductor also extends along the transmission line axis. In onevariation of an antenna, a length of transmission line is provided witha plurality of openings through which energy “leaks” or radiates awayfrom the transmission line or coaxial cable. This type of constructionis typically referred to as a “leaky coaxial” or “leaky wave” antenna. Aleaky wave antenna is basically a waveguiding structure constructed soas to “leak” power along the length of the guiding structure.

During certain procedures, it can be difficult to assess the extent towhich the microwave energy will radiate into the surrounding tissue,making it difficult to determine the area or volume of surroundingtissue that will be ablated.

SUMMARY

The present disclosure relates to a device for directing energy to atarget volume of tissue including an antenna assembly and an elongatedbody member. The elongated body member includes a proximal end portionand a distal end portion, wherein the proximal and distal end portionsdefine a longitudinal axis, the elongated body member having a body walldefining a chamber therein. The antenna assembly is disposed in thechamber. The elongated body member also includes an opening in the bodywall to allow energy radiated from the antenna assembly to transfer intothe target volume of tissue.

The present disclosure also relates to an ablation applicator includinga catheter assembly and an antenna assembly. The catheter assemblyincludes a tubular body member having an outer surface. The outersurface of the tubular body member includes an aperture formedtherethrough. At least one of the catheter assembly and the outersurface of the tubular body member is formed of an electricallyconductive material. The antenna assembly is disposed in the tubularbody member of the catheter assembly. The aperture in the outer surfaceof the tubular body member is configured to allow energy to radiate fromthe antenna assembly in a directional broadside radiation pattern.

The present disclosure also relates to a method for directing energy toa target volume of tissue including the steps of providing a deviceincluding an elongated body member having a body wall defining a chambertherein, and an antenna assembly disposed in the chamber, wherein theelongated body member includes an opening in the body wall, andpositioning the device to the target volume of tissue. The method alsoincludes the steps of transmitting energy from an energy source to theantenna assembly, and causing the energy to radiate through the openingin a broadside radiation pattern to the target volume of tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects and features of the presently disclosed antenna assemblies willbecome apparent to those of ordinary skill in the art when descriptionsof various embodiments thereof are read with reference to theaccompanying drawings, of which:

FIG. 1 is a schematic diagram of an ablation system according to anembodiment of the present disclosure;

FIG. 2 is a partial, longitudinal cross-sectional view of an energyapplicator of the ablation system shown in FIG. 1 according to anembodiment of the present disclosure;

FIG. 3 is an enlarged view of the indicated area of detail of FIG. 2according to an embodiment of the present disclosure;

FIG. 4 is a partial, longitudinal cross-sectional (split) view of anelongated body member configured to receive the energy applicator ofFIG. 2 according to an embodiment of the present disclosure;

FIG. 5 is a partial, perspective view of an electrosurgical deviceincluding the elongated body member of FIG. 4 shown with the energyapplicator of FIG. 2 (in phantom lines) disposed therein according to anembodiment of the present disclosure;

FIG. 6 is partial, longitudinal cross-sectional view of theelectrosurgical device of FIG. 5 according to an embodiment of thepresent disclosure;

FIG. 7 is a schematic diagram of an ablation system including theelectrosurgical devices of FIGS. 5 and 6 according to an embodiment ofthe present disclosure;

FIG. 8 is a schematic diagram of the electrosurgical device of FIGS. 5through 7 shown with indicia graduation marks and an indicia alignmentmark according to an embodiment of the present disclosure;

FIGS. 9 and 10 are schematically-illustrated representations ofsimulation results showing broadside radiation patterns according toembodiments of the present disclosure; and

FIG. 11 is a flowchart illustrating a method of directing energy to atarget volume of tissue according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the presently disclosed electrosurgicaldevice with a directional radiation pattern will be described withreference to the accompanying drawings. Like reference numerals mayrefer to similar or identical elements throughout the description of thefigures. As shown in the drawings and as used in this description, andas is traditional when referring to relative positioning on an object,the term “proximal” refers to that portion of the apparatus that iscloser to the user and the term “distal” refers to that portion of theapparatus that is further from the user.

Electromagnetic energy is generally classified by increasing energy ordecreasing wavelength into radio waves, microwaves, infrared, visiblelight, ultraviolet, X-rays and gamma-rays. As it is used in thisdescription, “microwave” generally refers to electromagnetic waves inthe frequency range of 300 megahertz (MHz) (3×10⁸ cycles/second) to 300gigahertz (GHz) (3×10¹¹ cycles/second). As it is used in thisdescription, “ablation procedure” generally refers to any ablationprocedure, such as microwave ablation or microwave ablation assistedresection. As it is used in this description, “transmission line”generally refers to any transmission medium that can be used for thepropagation of signals from one point to another.

Various embodiments of the present disclosure provide electrosurgicaldevices for treating tissue and methods of directing electromagneticradiation to a target volume of tissue. Embodiments may be implementedusing electromagnetic radiation at microwave frequencies or at otherfrequencies. An electrosurgical system including an energy applicator,according to various embodiments, is designed and configured to operatebetween about 500 MHz and about 10 GHz with a directional radiationpattern.

Various embodiments of the presently disclosed electrosurgical devicewith a directional radiation pattern are suitable for microwave ablationand for use to pre-coagulate tissue for microwave ablation assistedsurgical resection. Although various methods described hereinbelow aretargeted toward microwave ablation and the complete destruction oftarget tissue, it is to be understood that methods for directingelectromagnetic radiation may be used with other therapies in which thetarget tissue is partially destroyed or damaged, such as, for example,to prevent the conduction of electrical impulses within heart tissue. Inaddition, although the following description describes the use of adipole microwave antenna, the teachings of the present disclosure mayalso apply to a monopole, helical, or other suitable type of microwaveantenna.

FIG. 1 shows an electrosurgical system 10, according to an embodiment ofthe present disclosure, which includes an energy applicator or probe100. Energy applicator 100 includes an antenna assembly 12 that isconnected by a feedline 110 (or shaft) via a transmission line 15 to aconnector 16, which may further operably connect the probe 100 to apower generating source 28, e.g., a microwave or radio frequency (RF)electrosurgical generator. In some embodiments, the power generatingsource 28 is configured to provide microwave energy at an operationalfrequency from about 500 MHz to about 2500 MHz. In other embodiments,the power generating source 28 is configured to provide microwave energyat an operational frequency from about 500 MHz to about 10 GHz. Powergenerating source 28 may be configured to provide various frequencies ofelectromagnetic energy. Transmission line 15 may additionally oralternatively provide a conduit (not shown) configured to providecoolant from a coolant source 18 to the probe 100.

Located at the distal end of the antenna assembly 12 is an end cap ortapered region 120, which may terminate in a sharp tip 123 to allow forinsertion into tissue with minimal resistance. One example of a straightprobe with a sharp tip that may be suitable for use as the energyapplicator 100 is commercially available under the trademark Evident™offered by Covidien. The end cap portion or tapered region 120 mayinclude other shapes, such as, for example, a tip 123 that is rounded,flat, square, hexagonal, or cylindroconical.

In some variations, the antenna assembly 12 includes a distal radiatingportion 105 and a proximal radiating portion 140. A feedpoint or puck130 may be provided. In some embodiments, the puck 130, having length“L2”, is a junction member that couples the proximal radiating portion140 and the distal radiating portion 105. Puck 130, or portions thereof,may be disposed between the proximal and distal radiating portions, 140and 105. Puck 130 may be formed from any suitable elastomeric or ceramicdielectric material by any suitable process. In some embodiments, thepuck 130 is formed by overmolding and includes a thermoplasticelastomer, such as, for example, polyether block amide (e.g., PEBAX®,manufactured by The Arkema Group of Colombes, France), polyetherimide(e.g., ULTEM® and/or EXTEM®, manufactured by SABIC Innovative Plasticsof Saudi Arabia) and/or polyimide-based polymer (e.g., VESPEL®,manufactured by E. I. du Pont de Nemours and Company of Wilmington,Del., United States). Puck 130 may be formed using any suitableovermolding compound by any suitable process, and may include use of aceramic substrate.

In some embodiments, the antenna assembly 12 may be provided with acoolant chamber (not shown). Additionally, the puck 130 may includecoolant inflow and outflow ports (not shown) to facilitate the flow ofcoolant into, and out of, the coolant chamber. Examples of coolantchamber and coolant inflow and outflow port embodiments are disclosed incommonly assigned U.S. patent application Ser. No. 12/401,268 filed onMar. 10, 2009, entitled “COOLED DIELECTRICALLY BUFFERED MICROWAVE DIPOLEANTENNA”, and U.S. Pat. No. 7,311,703, entitled “DEVICES AND METHODS FORCOOLING MICROWAVE ANTENNAS”.

In some embodiments, the antenna assembly 12 may be provided with anouter jacket (not shown) disposed about the distal radiating portion105, the puck 130 and/or the proximal radiating portion 140. The outerjacket may be formed of any suitable material, such as, for example,polymeric or ceramic materials. The outer jacket may be applied by anysuitable method, such as, for example, heat shrinking, overmolding,coating, spraying dipping, powder coating, baking and/or filmdeposition.

During microwave ablation, e.g., using the electrosurgical system 10,the probe 100 is inserted into or placed adjacent to tissue andmicrowave energy is supplied thereto. Ultrasound or computed tomography(CT) guidance may be used to accurately guide the probe 100 into thearea of tissue to be treated. Probe 100 may be placed percutaneously orsurgically, e.g., using conventional surgical techniques by surgicalstaff. A clinician may pre-determine the length of time that microwaveenergy is to be applied. Application duration may depend on many factorssuch as tumor size and location and whether the tumor was a secondary orprimary cancer. The duration of microwave energy application using theprobe 100 may depend on the progress of the heat distribution within thetissue area that is to be destroyed and/or the surrounding tissue.Single or multiple probes 100 may provide ablations in short proceduretimes, e.g., a few minutes, to destroy cancerous cells in the targettissue region.

A plurality of probes 100 may be placed in variously arrangedconfigurations to substantially simultaneously ablate a target tissueregion, making faster procedures possible. Multiple probes 100 can beused to synergistically create a large ablation or to ablate separatesites simultaneously. Tissue ablation size and geometry is influenced bya variety of factors, such as the energy applicator design, number ofenergy applicators used simultaneously, time and wattage.

Referring to FIGS. 2 and 3, an embodiment of the antenna assembly 12 ofFIG. 1 is shown and includes an inner conductor 210, having length “L3”,an outer conductor 260, having length “L1”, and may include a firstdielectric material 240 separating the inner conductor 210 and the outerconductor 260. In some embodiments, the inner conductor 210 is formedfrom a first electrically conductive material (e.g., stainless steel)and the outer conductor 260 is formed from a second electricallyconductive material (e.g., copper). In some embodiments, the outerconductor 260 coaxially surrounds the inner conductor 210 along a distalportion of the antenna assembly 12, having length “L1”, as shown in FIG.2. Inner conductor 210 and the outer conductor 260 may be formed fromany suitable electrically conductive material.

First dielectric material 240 may be formed from any suitable dielectricmaterial, including, but not limited to, ceramics, water, mica,polyethylene, polyethylene terephthalate, polyimide,polytetrafluoroethylene (PTFE) (e.g., Teflon®, manufactured by E. I. duPont de Nemours and Company of Wilmington, Del., United States), glass,or metal oxides. Antenna assembly 12 may be provided with a seconddielectric material 290 surrounding the outer conductor 260 and/or thepuck 130, or portions thereof. Second dielectric material 290 may beformed from any suitable dielectric material. In some embodiments, thesecond dielectric material 290 is formed form a material with adielectric constant different than the dielectric constant of the firstdielectric material 240.

In some embodiments, the antenna assembly 12, having length “L4”,includes a conductor end portion 280, which may be formed from anysuitable electrically conductive material. In some embodiments, theconductor end portion 280 is coupled to the inner conductor 210 and maybe formed of the same material as the inner conductor 210. As shown inFIG. 2, the conductor end portion 280 may be spaced apart a length “L2”from the outer conductor 260 by the puck 130, having length “L2”,disposed therebetween. Tapered region 120, or portions thereof maysurround a proximal portion of the conductor end portion 280. In someembodiments, the conductor end portion 280 is substantiallycylindrically shaped, and may be formed from stainless steel. The shapeand size of the conductor end portion 280 may be varied from theconfiguration depicted in FIG. 2. In some embodiments, at least aportion of the conductor end portion 280 is surrounded by the seconddielectric material 290.

FIG. 4 shows an elongated body member 400, according to an embodiment ofthe present disclosure, which is configured to receive an energyapplicator (e.g., 100 shown in FIG. 1), or portions thereof. Anelectrosurgical device that includes the elongated body member 400 isshown in FIGS. 5 and 6. In some embodiments, the elongated body member400 is substantially tubular, except for a tapered portion 420 taperingfrom the distal end thereof. Tapered portion 420 may include a tipportion, which may be advantageously configured to facilitatepenetration of tissue. Although the surfaces of the tapered portion 420shown in FIGS. 4 through 6 are generally flat, the surfaces of thetapered portion 420 according to various embodiments may be curved ormay include a combination of flat, sloped or curved portions. The shapeand size of the tapered portion 420 may be varied from the configurationdepicted in FIGS. 4 through 6.

Elongated body member 400 includes a proximal end portion, a distal endportion, wherein the proximal and distal end portions define alongitudinal axis “A-A”, a chamber 480 surrounding and extending alongthe axis “A-A”, and a body wall 450 surrounding the chamber 480. Chamber480 is configured to receive at least a portion of an energy applicator(e.g., 100 shown in FIG. 1). In some embodiments, the chamber 480 isdimensioned and configured to receive an antenna assembly (e.g., 12shown in FIGS. 5 and 6) within the chamber 480. The shape and size ofthe chamber 480 may be varied from the configuration depicted in FIGS. 5and 6.

Body wall 450 is provided with at least one opening 440 therethrough toallow electromagnetic energy radiated from the energy applicator totransfer into the target volume of tissue (e.g., “T” shown in FIG. 7).In some embodiments, the opening 440 is configured for radiating energyin a broadside radiation pattern, such as the non-limiting exampledirectional radiation patterns shown in FIGS. 9 and 10. As shown inFIGS. 4 and 5, a substantially slot-shaped opening 440, having length“L5” and width “W”, may be positioned at a side portion of the body wall450, and may have a longitudinal axis that extends substantiallyparallel to the axis “A-A”. The shape and size of the opening 440 may bevaried from the configuration depicted in FIGS. 4 and 5.

Elongated body member 400 may include a plurality of openings 440. Insome embodiments, the body wall 450 is provided with a plurality ofelongated slots, which may be spaced longitudinally along the elongatedbody member 400. The size, shape and/or location of each opening 440 maybe based on the wavelength of the radiated energy along the antennaradiating portion (e.g., 140 and/or 105 shown in FIG. 2). The number ofopenings 440 may be based on various factors, such as, for example, thevolume of target tissue to be treated, the desired procedure, thewavelength of the electromagnetic energy to be radiated, and the shapeand/or dimensions of the openings. The size and/or shape of each opening440 may be based on the location of the opening 440 relative to a distaltip of the antenna assembly 12. In some embodiments, the antennaassembly 12 is a dipole antenna, and the openings 440 may be configuredto encompass any radial angle, length, and positioning with respect tothe antenna dipole arms.

Opening 440 may be provided with an electrically nonconductive material442. Nonconductive material 442 may include a nonconductive RFtransparent material, e.g., a glass fiber epoxy composite or polyimide.In some embodiments, the nonconductive material 442 substantiallyentirely fills the recess or void formed by the opening 440 in theelongated body member 400. Opening 440 may be filled with thenonconductive material 442 such that the external surface of theelongated body member 400 is substantially smooth.

Elongated body member 400 may include an outer jacket (e.g., 458 shownin FIGS. 5 and 6). Outer jacket 458 may be formed of any suitableelectrically conductive material, such as, for example, electricallyconducting metallic ceramic and polymeric electrically conductivematerials. Outer jacket 458 may include metal and/or conductive oxidelayers. Outer jacket 458 may be configured to surround the body wall450, or portions thereof, and/or the tapered portion 420, or portionsthereof. In some embodiments, the outer jacket 458 is formed of anelectrically conductive material and configured to substantiallysurround the body wall 450, except for the opening 440 and theelectrically nonconductive material 442 disposed therein.

Elongated body member 400 may be a tubular body (e.g. a tubular bodymember of a catheter assembly) having an outer surface (e.g., 458 shownin FIGS. 5 and 6) that includes a single or multiple openings 440 formedtherethrough. In some embodiments, the tubular body member is formed ofan electrically conductive material and/or the outer surface of thetubular body member is formed of an electrically conductive material.

FIGS. 5 through 7 show an electrosurgical device 500, according to anembodiment of the present disclosure, which is configured to operatewith a directional radiation pattern. Electrosurgical device 500includes the elongated body member 400 of FIG. 4 and the antennaassembly 12 of FIG. 2 disposed within the chamber 480 of the elongatedbody member 400. Antenna assembly 12 and the elongated body member 400may be disengageably coupled to each other. Electrosurgical device 500may be sufficiently small in diameter to be minimally invasive of thebody, which may reduce the preparation time of the patient as might berequired for more invasive penetration of the body.

Electrosurgical device 500 may include a moveable sleeve member (notshown) associated with elongated body member 400 and coaxially alignedwith the axis “A-A”. Such a sleeve member may either be on the outsideor the inside of elongated body member. In some embodiments, the sleevemember may be adapted to be rotationably moveable and/or slideablymoveable along the outside of the antenna assembly 12 to various axialpositions or various rotational positions to vary the size of theopening 440 with rotation angle. The sleeve member may include aplurality of apertures and may be moveable relative to the elongatedbody member 400 to various positions, thereby providing variablydimensioned electromagnetic “windows” within the opening 440. In otherembodiments, the elongated body member 400 itself may be adapted to berotationably moveable and/or slideably moveable along the outside of theantenna assembly 12.

FIG. 7 shows an electrosurgical system 700, according to an embodimentof the present disclosure, which includes the electrosurgical device 500of FIGS. 5 and 6. Electrosurgical device 500 is coupled to a connector16 via a transmission line 15, which may further connect theelectrosurgical device 500 to a power generating source 28, e.g., amicrowave or RF electrosurgical generator. During a procedure, e.g. anablation, the electrosurgical device 500 of the electrosurgical system700 is inserted into or placed adjacent to tissue “T” and energy issupplied thereto. Electrosurgical device 500 may be placedpercutaneously or surgically. Ultrasound or computed tomography (CT)guidance may be used to accurately guide the electrosurgical device 500into the area of tissue “T” to be treated.

FIG. 8 shows an electrosurgical device 800, which is similar to theelectrosurgical device 500 of FIGS. 5 through 7, except for the indiciaalignment mark 810 and the indicia graduation marks 880 on the proximalend of the electrosurgical device 800. Indicia alignment mark 810 and/orthe indicia graduation marks 880 may be carried on or inscribed into theelongated body member of the electrosurgical device 800. In someembodiments, the electrosurgical device 800 includes a plurality ofindicia graduation marks 880 defining units of linear measure, which maybe inscribed substantially circumferentially about the elongated bodymember. Indicia graduation marks 880 may be used to indicate therelative position of the opening 440 with respect to the surface of thetissue “T”. In some embodiments, the indicia graduation marks 880 areused to indicate the position of the distal end of the opening 440relative to the surface of the tissue “T”. Indicia graduation marks 880may be arranged to form an incremental pattern using any standardmeasure of length, e.g., inches or centimeters.

In some embodiments, the electrosurgical device 800 includes an indiciaalignment mark 810, e.g., a colored stripe, which is readily visiblealong the proximal end of the elongated body member. Indicia alignmentmark 810 is positioned on the elongated body member such that thelongitudinal axis of the alignment mark 810 substantially aligns withthe longitudinal axis of the opening 440, to provide a visual cue to thesurgeon to allow orientation of the direction of flow of the energy tocoincide with the indicia alignment mark 810. As shown in FIG. 8, one ormore of the indicia graduation marks 880 may overlap the indiciaalignment mark 810. The shape and size of the indicia alignment mark 810and the indicia graduation marks 880 may be varied from theconfigurations depicted in FIG. 8.

FIGS. 9 and 10 are schematically-illustrated representations ofsimulation results showing directional radiation patterns. Theillustrated results are based on a simulation that modeled operation ofan electrosurgical device 600, which is configured to operate with adirectional radiation pattern. Electrosurgical device 600 shown in FIGS.9 and 10 is similar to the electrosurgical device 500 of FIGS. 5 through7 and further description thereof is omitted in the interests ofbrevity.

FIG. 11 is a flowchart illustrating a method of directing energy to atarget volume of tissue, according to an embodiment of the presentdisclosure. In step 1110, an electrosurgical device (e.g., 500 shown inFIGS. 5 through 7) is provided, wherein the device includes an elongatedbody member (e.g., 400 shown in FIG. 4) having a body wall defining achamber therein, and an antenna assembly disposed in the chamber,wherein the elongated body member includes an opening (e.g., 440 shownin FIG. 7) in the body wall.

In step 1120, the device is positioned to the target volume of tissue.The electrosurgical device may be inserted directly into tissue (e.g.,“T” shown in FIG. 7), inserted through a lumen, e.g., a vein, needle orcatheter, placed into the body during surgery by a clinician, orpositioned in the body by other suitable methods known in the art. Theelectrosurgical device is configured to operate with a directionalradiation pattern. In some embodiments, the electrosurgical device isconfigured to operate with a broadside radiation pattern. In otherembodiments, the catheter or needle contains the opening to allow adirectional radiation pattern.

In step 1130, energy from an energy source (e.g., 28 shown in FIG. 7) istransmitted to the antenna assembly. For example, the energy source maybe any suitable electrosurgical generator for generating an outputsignal. In some embodiments, the energy source is a microwave energysource, and may be configured to provide microwave energy at anoperational frequency from about 500 MHz to about 10 GHz.

In step 140, the energy from the energy source is caused to radiatethrough the opening in the elongated body member. In some embodiments,the opening is configured for radiating energy in a broadside radiationpattern.

The above-described electrosurgical devices for treating tissue andmethods of directing electromagnetic radiation to a target volume oftissue may be used to provide directional microwave ablation, whereinthe heating zone may be focused to one side of the electrosurgicaldevice, thereby allowing clinicians to target small and/or hard tumorswithout having to penetrate the tumor directly or kill more healthytissue than necessary. The presently disclosed electrosurgical devicesmay allow clinicians to avoid ablating critical structures, such aslarge vessels, healthy organs or vital membrane barriers, by placing theelectrosurgical device between the tumor and critical structure anddirecting the electromagnetic radiation toward the tumor and away fromthe critical structure.

Although embodiments have been described in detail with reference to theaccompanying drawings for the purpose of illustration and description,it is to be understood that the inventive processes and apparatus arenot to be construed as limited thereby. It will be apparent to those ofordinary skill in the art that various modifications to the foregoingembodiments may be made without departing from the scope of thedisclosure. For example, with reference to FIGS. 4 and 5, theelectrosurgical device 500 may be rotatable about axis “A-A” such thatthe directional radiation pattern rotates therewith.

1. A device for directing energy to a target volume of tissue,comprising: an elongated body member, including: a proximal end portion;and a distal end portion, wherein the proximal and distal end portionsdefine a longitudinal axis, the elongated body member having a body walldefining a chamber therein; and an antenna assembly disposed in thechamber, wherein the elongated body member includes an opening in thebody wall to allow energy radiated from the antenna assembly to transferinto the target volume of tissue.
 2. The device of claim 1, wherein thebody wall includes an inner surface not in contact with tissue and anouter surface in contact with tissue when disposed in vivo, the innersurface of the body wall surrounding the chamber.
 3. The device of claim1, wherein the elongated body member is a substantially tubular body. 4.The device of claim 1, wherein the antenna assembly and the elongatedbody member are disengageably coupled to each other.
 5. The device ofclaim 1, wherein the opening is substantially filled with anelectrically nonconductive material.
 6. The device of claim 5, whereinthe elongated body member further includes an outer jacket formed of anelectrically conductive material.
 7. The device of claim 6, wherein theouter jacket is configured to substantially surround the body wall,except for the opening and the electrically nonconductive materialdisposed therein.
 8. The device of claim 7, wherein electricallynonconductive material is substantially transparent to radio frequency(RF) energy.
 9. The device of claim 1, wherein the elongated body memberfurther includes a tip disposed at the distal end portion configured topenetrate tissue.
 10. The device of claim 1, wherein a longitudinal axisof the opening in the body wall extends substantially parallel to thelongitudinal axis defined by the proximal and distal end portions of theelongated body member.
 11. The device of claim 1, further comprising anouter sleeve associated with the elongated body member, the outer sleeveconfigured to move rotationably or slideably along an outside of theantenna assembly.
 12. An ablation applicator, comprising: a catheterassembly, wherein the catheter assembly includes a tubular body memberhaving an outer surface, the outer surface including an aperture formedtherethrough, wherein at least one of the catheter assembly and theouter surface of the tubular body member is formed of an electricallyconductive material; and an antenna assembly, the antenna assemblydisposed in the tubular body member of the catheter assembly, whereinthe aperture in the outer surface of the tubular body member isconfigured to allow energy to radiate from the antenna assembly in abroadside radiation pattern.
 13. The ablation applicator of claim 12,wherein the aperture is substantially filled with an electricallynonconductive material.
 14. A method of directing energy to a targetvolume of tissue, comprising the steps of: providing a device includingan elongated body member having a body wall defining a chamber therein,and an antenna assembly disposed in the chamber, wherein the elongatedbody member includes an opening in the body wall; positioning the deviceto the target volume of tissue; transmitting energy from an energysource to the antenna assembly; and causing the energy to radiatethrough the opening in a broadside radiation pattern to the targetvolume of tissue.
 15. The method of claim 14, wherein the energy sourceis a microwave energy source configured to provide microwave energy atan operational frequency from about 500 MHz to about 10 GHz.
 16. Themethod of claim 14, further comprising varying the size of the openingvia an outer sleeve.